How does the presence of a union influence the job of the HR professional?

What will the role of labor unions be in the twenty-first century? Some argue that the traditional role of the union in protecting the worker has been usurped by significant legislation protecting the worker against discrimination, unsafe work conditions, and unfair pay. Others point out that at-will employment is the law of the land and most workers can be fired for any reason so unions remain indispensable.

For this discussion, respond to the following:

Does the modern union need to redefine its role and purpose to effectively serve its membership?How does the presence of a union influence the job of the HR professional?